Ultrawideband Microwave Absorber Conformable on Nondevelopable Curved Surfaces Based on the Hauberk Structure

In this paper, we propose a low-profile and ultra-wideband microwave absorber that is non-developable curved surface conformable, polarization insensitive, and wide-angle incidence insensitive. The absorptivity of the absorber is greater than 90% in (1.27-18.75) GHz and (1.3-18.93) GHz for TE and TM mode vertical incidence, respectively. The relative absorption bandwidth is 174.6% and 174.3%, respectively, both covering the entire S, C, X, and Ku bands. The absorber consists of a unique stainless-steel hauberk structure, a regular prismoid resistor sheet, and a 3-layer square resistor sheet supported by polymethacrylimide (PMI) foam. Notably, the absorber's thickness is only 0.093 times of the highest operating wavelength at 1.27 GHz. In the (2-18) GHz band, the absorptivity is > 80% for the TE mode within 60° incidence angle, and >85% for the TM mode within 80° incidence angle. When conformed to the surface of a standard metal sphere with a radius of 100mm, the absorber demonstrated excellent non-developable curved surface conformability and achieved >5dB radar cross section (RCS) reduction for both TE and TM mode incidence waves. This unique property makes the absorber ideal for applications with irregular and non-developable curved surfaces.